Visible capacity for understanding (7)
I believe the answer is:
insight
I believe this clue is a double definition.
'visible' is the first definition.
(something in sight is visible)
'capacity for understanding' is the second definition.
(insight is understanding things)
(Other definitions for insight that I've seen before include "Special knowledge" , "vision" , "Awareness" , "Practical knowledge" , "Clear understanding" .)